Trucks, trailers, railcars, baggage carts and the like have beds upon which cargo is carried.
Typically, the beds have a mostly flat or tabular surface and must be open and accessible for loading and unloading cargo, but otherwise covered during transportation and storage to keep rain, snow and dirt from the cargo, and/or keep debris from the cargo from escaping. A tarp is, therefore, used to cover the cargo when in transit.
Various tarp enclosure systems for truck beds and the like are known. In one enclosure system shown in U.S. Pat. No. 5,152,575 to DeMonte et al, which issued Oct. 6, 1992, a flexible tarp is secured to a series of bows which span the width of the bed. The bows are supported by wheels which are movable along upwardly open U-shaped tracks mounted underneath the side portions of the bed. The support wheels for the bows are rotatable in the U-shaped channels to guide the bows in longitudinal movement along the bed, permitting the tarp to be extended over the bed or collapsed in an accordion-like manner.
A difficulty with conventional tarp enclosure systems exists in that mounting of the channels beneath the bed limits the radial diameter of the support wheels which may be used to the spacing between the track and the underside of the bed. Typically, therefore, conventional tarp systems incorporate one or more 1 or 2" diameter wheels to movably support the bows. The smaller sized wheels tend to bind in the U-shaped channels and are poorly adapted to withstand the higher loads associated with larger bow systems and heavier tarps, making it difficult to slide the bows along the tracks. In this regard, in the prior art, the use of complex pulleys and cable drive systems are generally required to assist in moving the bows along the tracks, complicating manufacture and installation and adding to the overall cost of the tarp enclosure system.
A further difficulty with conventional enclosure systems exists in that the upwardly open U-shaped tracks are particularly prone to the accumulation of leaves, dirt, snow, ice and other such debris therein. The accumulation of debris in the U-shaped tracks or channels interferes with the rotation of the support wheels therein and hinders longitudinal movement of the bows along the track.
In addition, as the tracks are mounted along the underside of the bed, conventional tarp enclosure systems cannot be installed in a variety of existing stepped truck, train and/or trailer beds, which have vertically displaced horizontal surfaces.
On some vehicles, there is only a few inches of space between the tops of the tires and the bottom of the rub rail. Taking the suspension travel into account leaves very little space for mounting tracks along the underside of the bed. In extreme cases, there is no space available at all.
Another difficulty exists in that when the tracks are installed underneath the bed, the tarp covers the sides of the truck bed and the bed rub rail when the tarp is in place extended over the bed. In the extended position, the tarp thereby obscures any reflectors, running lights or reflective material positioned along the sides of the bed as a visual warning apparatus, creating a potential traffic hazard.